The sensation of sound involves a variety of factors in addition to its speak level. Advertisers are skilful at creating the impression of loudness through their expert use of such factors. One major contributor to the perceived loudness of commercials is that mush less variation in sound level occurs during a commercial. In regular programming the intensity of sound varies over a large range. However, sound levels in commercials tend to stay at or near peak levels.
最后两句话的大意是：在普通节目中，声音的强度变化很大。然而，在广告中，声音始终保持在峰值。
根据这两句话的提示，我们可以推断广告听起来吵的原因便是声音始终保持在峰值，没有强度的变化。因此，32题的B选项“Their sound levels are kept around peak levels.” (声音始终保持在峰值)是正确选项。
二、表示因果关系的词汇
出题者十分热衷于针对文章中表示因果关系的语句出题，这样的语句应当引起阅读者的注意，阅读者应当把握原因和结果分别指代什么文章信息。表示因果关系的词可作如下分类：
1、名词：base, basis, result, consequence, reason
2、动词：cause, result in, result from, follow from, base on, be due to
3、介词或连词：because, since, for, as, therefore, so, thus, why, with
4、副词：as a result, consequently
例 1 ：四级2002年6月39题：
39. People were given physical fitness tests in order to find out ________.
A) how well they could do in athletics
B) what their health condition was like
C) what kind of fitness center was suitable for them
D) whether they were fit for aerobic exercise
39题考查对人们进行体能测试的目的。根据关键词“physical fitness tests”，我们可以将考题定位至原文第二段，在第二段首句我们发现了因果关系标志词“because”，二段首句就是我们要寻找的答案，阅读者应当注意阅读“because”后的原因内容。
Historically, most physical-fitness tests have usually included measures of muscular strength and endurance, not for health-related reasons, but primarily because such fitness components have been related to performance in athletics. However, in recent years, evidence has shown that training programs designed primarily to improve muscular strength and endurance might also offer some health benefits as well. The American College of Sports Medicine now recommends that weight training be part of a total fitness program for healthy Americans. Increased participation in such training is one of the specific physical activity and fitness objectives of Healthy People 2000: National Health Promotion and Disease Prevention Objectives.
二段首句的大意为：历史上，大多数体能测试通常包括肌肉力量测试和耐力测试，这并不是要看谁更健康，主要是因为这些体能指标与体育成绩有关。